Many aged tequilas are hitting on the market that are decolorized. After aging for a certain amount of time they picked up color from the barrels. Then these were filtered to make them clear again. This is quite common in white rum, and now increasingly common in tequila.
Here is a list of the ones I know about.
Qui Tequila - "The world's first platinum extra añejo tequila...Qui undergoes a proprietary filtration and distillation" link
Casa Dragones - A blend of blanco with anejo tequila. "The brilliant platinum color of Casa Dragones, which heralds the delicate aroma, is achieved using an ultra-modern filtration system." link
Don Julio 70 Anejo Claro- Clarified anejo tequila link
Milagro Unico -"Milagro Unico combines our exclusive, micro-distilled silver tequila with our rarest and finest barrel-aged reserves to create a smooth, complex joven blend." link
Maestro Dobel Diamon Tequila- A blend of reposado, anejo, and extra-anejo. "Each bottle of Dobel Tequila is double-distilled, matured in Hungarian White Oak barrels, and filtered for exceptional smoothness and clarity." link
Lunazul Primero - "Filtered eight times to achieve a crystal clear color, Primero is a unique Añejo Tequila with flawless color and unusual maturity." link
- Herradura Ultra - Previously only available in Mexico at 35% ABV, now (June 2015) launched in the USA at 40%. "Casa Herradura’s Añejo tequila provides the base for Herradura Ultra. The Añejo is blended with premium Extra Añejo that has been aged for up to 49 months in American White Oak barrels. A subtle hint of agave nectar is added before the liquid is filtered."
Alacran Cristal Tequila "Alacran Cristal is an anejo tequila that uses agaves from 7-10 years old harvested in the highlands of Jalisco. It is matured for 14 months in American Oak barrels from bourbon, then put through an exclusive clarifying filtration process. It retails for $49.00-$59.00."
Some tequilas are clarified through a different method: redistilling. Corzo is aged and redistilled, and so are some of the high-end Patron tequilas. I believe that this resets the aging, so that an aged tequila destilled becomes a blanco again.
About Clarifying Spirits
Clarifying aged spirits is very common in rum: most white rum is aged for a year or more and then filtered through charcoal to remove most of the color. But it's relatively new in tequila. I belive Maestro Dobel was the first to do it.
For more about filtration in spirits, check out this article I wrote about filtration in all spirit categories for DiffordsGuide.com.